R. Garcia-Gil

A Synchronous Reference Frame Robust Predictive Current Control for Three-Phase Grid-Connected Inverters

This paper presents a new predictive current control for three-phase grid-connected inverters in the synchronous reference frame. The control combines a deadbeat control law with a diagonal Luenberger observer to estimate the future value of the grid currents. It provides a decoupled control of the active and reactive power and offers robustness against the computational delay inherent in the digital implementation and against filter and grid-impedance uncertainties. This control exhibits a very fast current response while widely improving the gain and phase margins of the traditional predictive controllers.

An Adaptive Robust Predictive Current Control for Three-Phase Grid-Connected Inverters

This paper presents an adaptive robust predictive current control (RPCC) for grid-connected three-phase inverters that exhibit zero steady-state current error. The error correction is achieved by means of an adaptive strategy that works in parallel with the deadbeat algorithm, therefore preserving the typical fast response of the predictive law. The resulting control adapts to any particular L or LCL filter by estimation of the resistive part of the filter. As a variety of the RPCC class of control, it offers the best tradeoff between robustness and speed.

A bidirectional and isolated three-phase rectifier with soft-switching operation

A bidirectional-power-flow three-phase rectifier with high-frequency isolation and all-digital control, based on the matrix converter topology, is analyzed in this paper. The selected topology consists of a bidirectional three-phase-to-single-phase reduced matrix converter with power-factor correction and a bidirectional active rectifier. The inclusion of the isolation transformer at the switching frequency permits the reduction of volume and weight. By synchronizing the commutation of both converters and adding a saturable inductor and a blocking capacitor it is possible to achieve soft commutation for most of the semiconductor elements. An all-digital control based on a digital-signal-processor and a field-programmable gate array was used to implement space-vector modulation and output current regulation. This power converter is intended to feed the low-energy correction magnet of a particle accelerator. Experimental results of a 1.5-kW 20-kHz prototype are presented to illustrate the performance of the proposed topology.

A New Generalized Robust Predictive Current Control for Grid-Connected Inverters Compensates Anti-Aliasing Filters Delay

In this paper, a new predictive control for grid-connected inverters is presented, which provides the best performance in terms of transient response and stability margins when analog filters in current sensing circuits are used. These filters are necessary to avoid aliasing in the A/D conversion process, which causes an important ripple on injected current into the grid and increases the total harmonic distortion. However, predictive controls are very sensitive to delays on the acquisitions, so when such anti-aliasing filters are used a reduction of stability margins is produced and the transient response is affected. The proposed predictive control allows to compensate the effect of the filter, for any order and cutoff frequency, providing the best transient response in the reference tracking and the highest stability margins. Furthermore, a modification on the adaptive strategy of current error is proposed, which allows to work with single-phase grid-connected inverters. The proposed predictive control has been tested on a 3.3-kVA single-phase grid-connected inverter with LCL filter, using different anti-aliasing filters, obtaining in all cases, better results than those offered by other predictive controls recently published.

A DSP-controlled four-quadrant AC-DC matrix converter with high-frequency isolation

A four-quadrant AC-DC converter with high frequency isolation and all-digital control, based on the matrix converter topology, is analyzed in this paper. The selected topology consists of a bidirectional three-phase cycloconverter with power factor correction and a bidirectional active rectifier. The inclusion of the isolation transformer at the switching frequency permits to reduce volume and weight. Experimental and simulated results of a 1.5 kW, 20 kHz prototype proof the performance of the proposed topology.

Zero-current-switched three-phase SVM-controlled buck rectifier

A zero-current-transition (ZCT) cell is analyzed and designed to be used with a three-phase pulsewidth-modulation buck rectifier. This rectifier was space-vector controlled and used unidirectional current switches. The proposed ZCT circuit is load independent and achieves a high noise and voltage stress reduction and provides ZCTs to almost all transitions of the rectifiers switches and to the additional auxiliary switches. Theoretical equations have been obtained for design purposes. The circuit is easy to design and the driving signals for the auxiliary switches are also easy to obtain, as demonstrated in this paper.

New power MOSFET selection method to avoid failures

Power MOSFET are the primary cause of failure at high power inverters. The turning on of the parasitic bipolar transistor during hard turn off of the intrinsic body diode causes the failures. We propose to test MOSFET from different manufacturers under controlled laboratory conditions. The worst switching condition and the most robust MOSFET was then identified.

Soft switched interleaved boost converters used as high-power battery discharge regulator for space power systems

In the following years the telecommunication satellites will have a much greater power demand than nowadays. One reason for this is that the geostationary orbit required by this kind of satellites is becoming too crowded. Probably power levels of l0 kW to l00 kW will be the standard and with life duration of 25 years. It is not possible to keep 0.5 kW modules with more than 100 in parallel and therefore higher power modules (5 kW) must be used. A higher bus voltage seems also necessary and keeping a safety limit of 150 V, any voltage below it and above 100 V could meet the needs. In this paper we will propose a topology that fits the application: two soft switched interleaved boost converters with peak current control. Design guidelines and experimental results will be presented.

Obtaining the Electrical Model of a Power Transformer by Means of Finite Element Software

Abstract. The behaviour of transformers and inductors working at high-frequencies and high power density can dramatically differ from the ideal or low-frequency operation. Their performance is very dependent on the magnetic material, operating frequency and physical construction. In this paper, finite element analysis (FEA) is used to obtain an accurate characterization of the electromagnetic behaviour of these magnetic components.

Parameterizing non-linear magnetic cores for PSpice Simulation

Abstract. In this paper the main Jiles & Atherton parameters of a magnetic material, according to their particular working condition (mainly frequency, temperature and waveform) are calculated by means of a systematic procedure that use PSpice and MathCad. The modelled magnetic material is used for power electronics circuit simulation, which uses magnetic materials, working at frequencies in the region of kH, to construct transformers and inductors. Magnetic materials are the most critical components in electronics simulators due to their nonlinear behaviour and the accuracy in the simulation can only be obtained through a proper magnetic material modelling. This paper examines the modelling of the magnetic core hysteresis for high-frequency applications. As example of application, a buck converter with its inductor working near saturation is implemented and its experimental waveforms are compared with that obtained by simulation.